In vitro stress measurements in the vicinity of six mechanical aortic valves using hot-film anemometry in steady flow

1988 ◽  
Vol 21 (3) ◽  
pp. 235-247 ◽  
Author(s):  
J.M. Hasenkam ◽  
D. Westphal ◽  
H. Nygaard ◽  
H. Reul ◽  
M. Giersiepen ◽  
...  
Keyword(s):  
Steady Flow ◽  
Aortic Valves ◽  
Stress Measurements ◽  
Hot Film ◽  
In Vitro Stress ◽  
Hot Film Anemometry

Non-Steady Flow Measurements Inside a Hydrodynamic Torque Converter by Hot-Film Anemometry

1992 ◽  
Author(s):  
V. Browarzik ◽  
K. G. Grahl
Keyword(s):  
Flow Field ◽  
Steady Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Measuring System ◽  
Pump Impeller ◽  
Flow Measurements ◽  
First Results ◽  
Hot Film ◽  
Hot Film Anemometry

The overall-characteristics of hydrodynamic torque converters have been discussed often, although there is little knowledge about the flow field inside the circuit. During former investigations at our institute flow measurements have been made and a CFD-program was developed to calculate the flow through the guide vanes and the pump impeller. Our present studies now examine the non-steady flow field at the inlet and outlet of the pump and the turbine impeller by means of hot-film anemometry and a computer based measuring system. The measuring techniques have been developed and now measurements are made at different operating points. Later the measurements will be performed with special regard to non-steady changes of operating conditions. The paper describes the test facilities, the measuring equipment and the techniques used to evaluate the measured data. First results of test measurements are presented.

Use of Hot-Film Anemometry for Wall Shear Stress Measurements in Unsteady Flows

2010 ◽  
Author(s):  
C. Ariyaratne ◽  
F. Wang ◽  
S. He ◽  
A. E. Vardy
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Unsteady Flows ◽  
Momentum Exchange ◽  
Reynolds Analogy ◽  
Initial Flow ◽  
Stress Measurements ◽  
Wall Shear ◽  
Hot Film ◽  
Hot Film Anemometry

Hot-wire and hot-film anemometry are widely used in steady flows for instantaneous velocity measurements, and their use has been extended to velocity and wall shear stress measurements in unsteady flows. The technique of hot-film anemometry relies on the Reynolds analogy which relates the diffusion of heat to the momentum exchange. The paper investigates the applicability of the analogy in linearly varying flows. The investigation is a combination of CFD analyses using the Transition SST model and experimental measurements. Results show that, in a linearly accelerating flow, while wall shear stress increases immediately upon the onset of acceleration, heat transfer indicates a relative lag in response. A quantitative analysis of the effects of flow parameters shows that the deviant behaviour is especially pronounced with increasing acceleration and/or reduced initial flow Reynolds number. The initial deviation can be predicted using a non-dimensional parameter based on turbulence timescales and acceleration rate, thereby providing a possible solution to correcting wall shear stress measurements using hot-film anemometry in fast accelerating flows.

Turbulent Stresses in the Region of Aortic and Pulmonary Valves

1982 ◽  
Vol 104 (3) ◽  
pp. 238-244 ◽  
Author(s):  
P. D. Stein ◽  
F. J. Walburn ◽  
H. N. Sabbah
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Blood Cells ◽  
Reynolds Shear Stress ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Reynolds Stresses ◽  
Aortic Valves ◽  
Hot Film

The specific features of turbulent flow that are likely to be damaging to the blood cells and platelets are the stresses which are intrinsic to turbulence, known as Reynolds stresses. These include normal stresses as well as shear stresses. The purpose of this study is to determine the magnitude of the turbulent stresses that may occur during ejection in the vicinity of normal and diseased aortic valves near normal pulmonary valves. Both Reynolds normal stresses and Reynolds shear stresses were calculated from velocities obtained in vitro with a laser Doppler anemometer in the region of two severely stenotic and regurgitant human aortic valves. Reynolds normal stresses were also calculated from velocities obtained with a hot-film anemometer in 21 patients in the region of normal and diseased aortic valves. In seven of these patients, it was calculated in the region of the normal pulmonary valve. The Reynolds normal stress in patients with combined aortic stenosis and insufficiency was prominently higher than in patients with normal valves. In the former, the Reynolds normal stress during ejection transiently reached 18,000 dynes/cm2. This was in the range of the Reynolds normal stress observed in vitro. The Reynolds shear stress measured in vitro transiently reached 11,900 dynes/cm2 during ejection. Because the Reynolds normal stresses in the presence of the severely stenotic and regurgitant valves were comparable in vitro and in patients, it is likely that the Reynolds shear stress in patients is also comparable to values measured in vitro. These values were well above the stresses which, when sustained, have been shown to have a damaging effect upon blood cells and platelets.

500 An in vitro steady flow model of mitral regurgitation by three-dimensional Doppler

1999 ◽  
Vol 1 ◽  
pp. S86-S86
Author(s):  
R DESIMONE ◽  
G GLOMBITZA ◽  
C VAHL ◽  
H MEINZER ◽  
S HAGL
Keyword(s):  
Mitral Regurgitation ◽  
Steady Flow ◽  
Flow Model ◽  
Three Dimensional

Platelet membrane-coated nanoparticles target sclerotic aortic valves in ApoE−/− mice by multiple binding mechanisms under pathological shear stress

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
H Yang ◽  
Y Song ◽  
Z Huang ◽  
J Qian ◽  
Z Pang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Aortic Valve ◽  
Aortic Valve Disease ◽  
Binding Capacity ◽  
Platelet Membrane ◽  
Valve Disease ◽  
Funding Source ◽  
Aortic Valves ◽  
Coated Nanoparticles

Abstract Background Aortic valve disease is the most common valvular heart disease leading to valve replacement. The efficacy of pharmacological therapy for aortic valve disease is limited by the high mechanical stress at the aortic valves impairing the binding rate. We aimed to identify nanoparticle coating with entire platelet membranes to fully mimic their inherent multiple adhesion mechanisms and target the sclerotic aortic valve of apolipoprotein E-deficient (ApoE−/−) mice based on their multiple sites binding capacity under high shear stress. Methods Considering the potent interaction of platelet membrane glycoproteins with components present in sclerotic aortic valves, platelet membrane-coated nanoparticles (PNPs) were synthetized and the binding capacity under high shear stress was evaluated in vitro and in vivo. Results Compared with PNPs bound intensity in the static station, 161%, 59%, and 39% of attached PNPs remained adherent on VWF-, collagen-, and fibrin-coated surfaces under shear stress of 25dyn/cm2 respectively. PNPs demonstrated effectively adhering to von Willebrand factor, collagen and fibrin under shear stresses in vitro. In an aortic valve disease model established in ApoE−/− mice, PNPs group exhibited significant increase of accumulation in the aortic valves compared with PBS and control NP group. PNPs displayed high degrees of proximity or co-localization with vWF, collagen and fibrin, which exhibited good targeting to sclerotic aortic valves by mimicking platelet multiple adhesive mechanisms. Conclusion PNPs could provide a promising platform for the molecular diagnosis and targeting treatment of aortic valve disease. Targeting combination Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): National Natural Science Foundation of China

Measurement of wall shear stress in physiological pulsatile flows by flush-mounted hot film anemometry

1988 ◽  
Vol 16 (2) ◽  
pp. 235-238
Author(s):  
Subhashis Nandy ◽  
Alex Yefim Bekker ◽  
Gregory Allen Winchell ◽  
John Francis O'Riordan
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulsatile Flows ◽  
Wall Shear ◽  
Hot Film ◽  
Hot Film Anemometry

scholarly journals Anti-Ace monoclonal antibody reduces Enterococcus faecalis aortic valve infection in a rat infective endocarditis model

2018 ◽  
Vol 76 (8) ◽  
Author(s):  
Kavindra V Singh ◽  
Kenneth L Pinkston ◽  
Peng Gao ◽  
Barrett R Harvey ◽  
Barbara E Murray
Keyword(s):  
Monoclonal Antibody ◽  
Infective Endocarditis ◽  
Enterococcus Faecalis ◽  
Collagen Iv ◽  
Aortic Valves ◽  
Collagen Binding ◽  
Passive Protection ◽  
A Cell ◽  
Pre Treatment

AbstractAce (Adhesin to collagen from Enterococcus faecalis) is a cell-wall anchored protein that is expressed conditionally and is important for virulence in a rat infective endocarditis (IE) model. Previously, we showed that rats immunized with the collagen binding domain of Ace (domain A), or administered anti-Ace domain A polyclonal antibody, were less susceptible to E. faecalis endocarditis than sham-immunized controls. In this work, we demonstrated that a sub nanomolar monoclonal antibody (mAb), anti-Ace mAb70, significantly diminished E. faecalis binding to ECM collagen IV in in vitro adherence assays and that, in the endocarditis model, anti-Ace mAb70 pre-treatment significantly reduced E. faecalis infection of aortic valves. The effectiveness of anti-Ace mAb against IE in the rat model suggests it might serve as a beneficial agent for passive protection against E. faecalis infections.

Sign in / Sign up

Export Citation Format

Share Document